Inside Ford’s Hidden Mid-Engine Boss 429 Mustang

Hidden Revolution - In the late 1960s, the American muscle car scene was buzzing with horsepower wars, each manufacturer pushing boundaries to dominate both streets and racetracks. Amid this golden era of automotive experimentation, Ford quietly embarked on a daring project that few knew existed: a mid-engine version of the legendary Boss 429 Mustang. This ambitious endeavor, developed under the radar, aimed to address a critical flaw in the production Boss 429—the unwieldy weight distribution caused by placing a massive iron-block V8 in the front of a short, lightweight chassis.

Red Ford’s Hidden Mid-Engine Boss 429 Mustang was an ambitious, under-the-radar experiment designed to fix the production car’s poor weight balance caused by its massive iron-block V8 up front. (Picture from: MacsMotorCityHarage)

The masterminds behind this hidden experiment were Ford’s Special Vehicles division, working alongside the Detroit-based Kar Kraft, a private skunkworks known for ingenious engineering solutions. Internally dubbed the LID Mustang, short for “Low Investment Drivetrain,” the project represented a resourceful approach: relocate the engine to the rear using mostly existing components, rather than investing in exotic, costly European transaxles. The goal was straightforward yet audacious—transform the Boss 429 into a more balanced, mid-engine powerhouse with minimal financial outlay. 

Red 1969 Ford’s Hidden Mid-Engine Boss 429 Mustang was developed by Ford’s Special Vehicles division and Kar Kraft as the LID Mustang, a low-cost concept that shifted the engine rearward using mostly existing components. (Picture from: MacsMotorCityHarage)

Engineering the LID Mustang required a bold reimagining of the vehicle’s layout. The standard Boss 429 engine and C6 automatic transmission were reversed and mounted on a custom rear subframe, sitting directly over the rear axle. A specialized transfer case, inspired by marine drives, rotated the output 180 degrees to feed a modified 9-inch Ford rear axle converted for independent operation. Articulated half shafts, u-joints, and a custom axle housing incorporated mounts for Koni coilover shocks and rear control arms, creating a modular, drop-out design that allowed for efficient assembly while maintaining structural integrity. 

Ford’s Hidden Mid-Engine Boss 429 Mustang reimagined its layout by reversing the Boss 429 engine and C6 automatic transmission and mounting them on a custom rear subframe over the rear axle. (Picture from: MacsMotorCityHarage)

On the exterior, the LID Mustang cleverly disguised its radical internals. It appeared nearly identical to a 1969 Mach I Sportsroof, complete with a conventional hood scoop up front. Its wheel setup was subtle yet effective: reverse-offset steel wheels—eight inches wide at the rear, six at the front—maintained stock track width and were hidden behind full Lincoln wheel covers. Inside, the rear seat was removed, replaced with black carpeting, while the front engine bay housed the battery, radiator, and air-conditioning condenser, all cooled by electric fans. The rear glass was replaced with a Sports Slat louver assembly that hinged upward, providing access to the relocated V8. 

Ford’s Hidden Mid-Engine Boss 429 Mustang reimagined its layout by reversing the Boss 429 engine and C6 automatic transmission and mounting them on a custom rear subframe over the rear axle. (Picture from: MacsMotorCityHarage)

The result was a striking reversal of the Boss 429’s weight distribution, flipping it from 60/40 front-heavy to 40/60 rear-biased. Yet, in a twist that surprised Ford engineers, the change produced little measurable improvement in overall performance, aside from reduced wheelspin. Despite this, the car functioned flawlessly on the street, demonstrating the ingenuity and precision of its builders. The LID Mustang exemplified a fascinating mix of creativity, practicality, and mid-century American engineering bravado. 

Ford’s Hidden Mid-Engine Boss 429 Mustang was developed by Ford’s Special Vehicles division and Kar Kraft as the LID Mustang, a low-cost concept that shifted the engine rearward using mostly existing components. (Picture from: MacsMotorCityHarage)

Historically, the LID Mustang holds a unique place as both a technological experiment and a glimpse into Ford’s willingness to challenge norms. While only one prototype was ever built, its story continues to captivate enthusiasts. Initial reports suggested it met the crusher at a Detroit salvage yard, but insiders later revealed that the car might have quietly vanished from Ford’s Dearborn Proving Grounds, tucked away in a private garage for decades. This air of mystery has cemented its legendary status, making it one of the most intriguing “what if” chapters in Mustang history. | C8Z1zzURLCM |

Today, the mid-engine Boss 429 stands as a testament to the bold, experimental spirit of late-1960s automotive design. It challenges assumptions about muscle car engineering, blending audacious ideas with practical execution. More than a forgotten prototype, the LID Mustang embodies an era when innovation often took the road less traveled, leaving behind stories that continue to ignite the imagination of car enthusiasts around the world. *** [EKA | FROM VARIOUS SOURCES | MACSMOTORCITYGARAGE | HOTCARS ]

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